Tectonic activities in the earth's interior, such as volcanic eruption and earthquake, take place frequently accompanied by variations in temperature and stress. Thus, to carry out long-term monitoring on the temperature and stress in the earth's interior, and build thermal-solid coupling dynamical models of the active tectonic zones for analysis of the data obtained therefrom, will help to further understand the dynamical mechanism of the tectonic activities, and provide theoretical basis for earthquake prevention in active tectonic zones.
The main active tectonic zones, such as the Longmenshan Fault Zone, the Chelongpu Fault Zone, the San Andreas Fault Zone, the Nankai Trough and the Japan Trench subduction zone, are subjected to long-term borehole monitoring. At present, during the long-term borehole monitoring on the active tectonic zones, temperature sensors, and stress or strain sensors, are mounted in the boreholes for monitoring the variations of temperature, stress and strain, respectively. However, in our experiments on the temperature response of crustal rocks to the stress change, it was found that the adiabatic pressure derivative of temperature (β=dT/dP) of most crustal rocks are usually low (only 2-6 mK/MPa). But the resolutions of the current temperature measurements are of the order of mK. Thus the temperature response could be detected only when the change of stress or strain is relatively great.
It is therefore necessary to improve the existing devices for monitoring temperature response to stress change in strata.